(1) Field of the Invention
The present invention relates to an improved method for color-intensifying in color photography, and more particularly, to a color-intensifying method for saving silver in color photography development, using a largely reduced amount of a processing solution.
(2) Description of Prior Art
A color-intensifying method has already been disclosed in detail in JP-A ("JP-A" means unexamined published Japanese patent application) Nos. 9728/1973, 9729/1973, 53826/1976, and 73731/1977, U.S. Pat. No. 3,816,134, and JP-A Nos. 13335/1977, and 127555/1980, and in particular, since the method of intensifying a photographic image in the presence of a nitrogen-containing compound that uses a peroxide, such as hydrogen peroxide, and a processing solution substantially free from iodide ions or bromide ions is high in the effect of intensifying a photographic image, an improvement thereof has been made by the instant inventors.
That is, after JP-A No. 18629/1983 filed by the inventors disclosed the above technique, improvements that include the omission of the washing step after the color-intensifying step (JP-A Nos. 137837/1983 and 127926/1983), improvements in various methods wherein intensifying processing solutions are applied to photographic materials (JP-A Nos. 80150/1986, 80149/1986, and 77851/1986), and improvements in steps of further increasing the image-intensification effect (JP-A No. 88259/1986) were made.
A major problem associated with the above prior techniques resides in that the image-intensification ratio changes conspicuously depend on the type and concentration of the halide ions involved. In other words, when iodide ions or bromide ions are present in the processing solution, the intensification effect decreases remarkably. However, a reducing solution free from iodide ions or bromide ions is not practical because such a solution causes great fogging in the photographic material. The inventors previously found that a nitrogen-containing heterocyclic compound can suppress fogging effectively without lowering the intensification effect (in some cases a nitrogen-containing heterocyclic compound rather improves the intensification effect), and suggested a method of intensifying a photographic image without causing fogging even when the processing solution does not contain iodide ions or bromide ions (JP-A No. 18629/1983). The photographic materials to which this technique is applied had no particular limitations on the halide composition of sliver salts, such as silver bromoiodide, silver bromide, silver chlorobromide, and silver chloride. This is because generally for the usual proportion of the amount of the photographic material to be processed to the amount of processing solution to be used, the amount of halide resulting from the photographic material for intensifying colors that contains less silver that has been applied is not enough to influence the halide concentration in the processing solution.
On the other hand, for the color-intensifying method disclosed in JP-A No. 18629/1983 suggested by the instant inventors, it could not be said that the processing solution has sufficient stability with time, because an oxidizing agent and a reducing agent are present in a single processing bath. With respect to the improvement in this stability with time, it is known that if an alkyl phosphonic acid, for example, typically hydroxyethane diphosphonic acid, a phosponocarboxylic acid, or an aromatic sulfonic acid is used, the life of the processing solution can be prolonged. It is also well known that when the processing solution in a processing tank is replaced with fresh processing solution, with the replacing ratio being high, its exhausting with time can be reduced. That is, when the replenishing solution is increased to increase the replacing ratio, and in an extreme case, when it is possible to discard the processing solution, the problem can be solved easily, but in that instance the amount of processing solution used will increase, which is less economical. However, the prior techniques could not help discarding the processing solution in the color-intensifying process for the stability of the processing solution, even though it was economically disadvantageous.
Therefore, the color intensification in the practical form involves discarding the processing solution, or keeping the processing solution replacing ratio high for continuous processing accompanied by replenishing. As means of decreasing the amount of processing solution to be used in this state, it is considered to make the processing tank smaller in discarding-type processing and in replenishing-type processing, which results in lowering the intensification effect of the photographic image. In other words, it was difficult to solve both the problem of exhausting of the processing solution and the problem of preventing the image intensification ratio from lowering.